Soay
sheep, perhaps the most primitive extant form of domestic sheep,
all come from the island of Soay. The origins of the Soay sheep
here are uncertain. The old Scandinavian name Sauda-ey means 'Island
of sheep', so they were probably present on the island of Soay in
Viking times (9th and 10th centuries AD).

Until 1932,
when a flock of 107 Soays were rounded up and moved onto Hirta,
pure-bred Soays were only found on the island of Soay.

All
Soay sheep in the world are descended from those found on the island
of Soay in the St Kilda archipelago. These small sheep are one of
the most primitive forms of domestic sheep in the world and have
probably remained virtually unchanged for thousands of years. No
one knows quite when the sheep arrived on St Kilda, but evidence
suggests they came with the first human settlers around 4000 years
ago. When the Norse arrived at the St Kilda archipelago in the 9th-10th
centuries AD they named the island Sauda-ey - 'Island of sheep'.
Until 1932 pure-bred Soays were only found on the island of Soay,
then a flock of 107 Soays were rounded up and moved onto the main
island of Hirta, Today flocks of Soay sheep are found all over the
world.

Today, unmanaged populations of Soays live on both Soay and Hirta
where their population fluctuations have interested biologists since
the 1950s.

Currently, researchers from from a number of universities and research
institutes participate in a multidisciplinary study of factors affecting
the population ecology of the sheep in St Kilda. This research has
recently been published:
Clutton Brock, T.H. & Pemberton J. (2004) Soay Sheep published
by Cambridge University Press. ISBN 0521823005

Running ram Photograph: Ken Wilson

Recording
courtesy of The British Library National Sound Archive

There are several study topics, ranging from investigating the relationship
between the Soay population and the Hirta vegetation, to asking
why it is that Soays vary genetically with respect to the presence
or absence of horns. Each year the lambs in the study area around
Village Bay are caught, measured, have blood samples taken and are
tagged before release. Once tagged an individual can be identified
easily and its progress watched for many years.

Some key
results of the project so far are:

Populations
of sheep on Hirta and Boreray fluctuate in synchrony.

Population declines result when high population density combines
with poor winter weather, but they are still very difficult to
predict.

Older,
normal-horned rams are most successful reproductively, but (as
revealed by DNA profiling) young and polled (hornless) rams also
frequently sire lambs.

More inbred Soays have lower resistance to nematode parasites
(worms) and are less successful reproductively.

Army personnel help to record details of a tagged lamb Photograph: Davina Graham